15 to Question 17 is based on this problem. A company has three warehouses that supply four stores with a given product. Each warehouse has 30 units of the product. Stores 1, 2, 3, and 4 require 20, 25, 30 and 35 units of the product, respectively. The per unit shipping costs from each warehouse to each store are given in the following table: Table 7 - Exam 2-1.png Note that all the demands from the four stores will not be fulfilled completely, because the total demand exceeds the total supply. Let Xij be the units of the product to be shipped from warehouse i to store j. Create a spreadsheet for this problem and solve it by Solver. Without including the nonnegativity constraints, how many constraints in total do we need for the LP formulation of this